Turkey's push to buy the S-400 system has strained relations with the United States, a NATO ally, which worries about integrating Russian technology with Turkey's Western equipment.

Defence Minister Hulusi Akar told reporters late Tuesday that Ankara was "preparing" for US penalties under the Countering America's Adversaries Through Sanctions Act (CAATSA), which prohibits business with Russia's state and private defence and intelligence sectors.

He added that Turkey was "fed up" with being just being a buyer of military equipment, and wanted to be involved in joint production and technology transfers.

"The idea that we always buy, you always produce, is finished," he told reporters in Ankara.

President Recep Tayyip Erdogan on Saturday said Turkey and Russia would jointly produce S-500 defence systems after the purchase of the S-400 system.

Turkey has already sent personnel to Russia for training, Akar said, and the system could be delivered as early as June or July.

Last month, he said the S-400 would likely be used to protect the capital Ankara and Istanbul.

In a bid to force Turkey to cancel its S-400 deal, the US offered a renewed proposal in March for Patriots, its own anti-missile and anti-aircraft weapon system.

The US has said buying the S-400 could jeopardise the Turkey's involvement in the F-35 fighter jet programme, for which it provides some parts.

Akar said Turkey was still considering the offer but that there had been "general easing" in negotiations with the US on the F-35s and Patriots.

Relations have been tense over multiple issues, including US support to a Syrian Kurdish militia viewed by Ankara as terrorists, and the refusal to extradite a Pennsylvania-based Muslim preacher Fethullah Gulen accused of ordering a failed coup in Turkey in 2016.